Optical disk apparatus

ABSTRACT

An optical disk apparatus includes: a light irradiator operable to converge a light beam and irradiate an information carrier with the converged light beam; a moving means operable to move the light beam in a direction traversing a track formed on a surface of the information carrier; and a tracking controller operable to control the moving means to scan the track with the light beam. The tracking controller includes a deviation detector operable to generate a detection signal, a tracking driving means operable to generate a driving signal, an integrator operable to integrate a magnitude of a signal corresponding to the driving signal over a predetermined time period and an abnormal state detector operable to detect an abnormal state of the moving means based on an output of the integrator.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to an optical diskapparatus for writing information to an information carrier (a recordingmedium) or reproducing information recorded on the information carrierby using a light beam from a light source, like a laser, moreparticularly, the present invention relates to an optical disk apparatusthat can detect an abnormal state of an actuator when a focusing controlor a tracking control is performed.

[0002] Now optical disk apparatuses that can record/reproduceinformation to/from an optical disk (information carrier or recordingmedium) having a recording layer formed of a phase-change medium or amagneto-optical medium have come into practical use. Such an opticaldisk apparatus irradiates a recording surface of the optical disk with alight beam converged by a converging lens (an objective lens) includedtherein so as to cause a phase change or inversion of magneticpolarization in the recording layer, thereby the information can berecorded onto the optical disk. As for the reproduction, the opticaldisk apparatus can reproduce the information from the optical disk bydetecting reflected light from the optical disk.

[0003] In the recording/reproduction operation mentioned above, thelight beam is to be subjected to a focusing control in order toaccurately place a converging point of the light beam on the recordingsurface of the optical disk. The focusing control is realized by movingthe converging lens in a direction substantially perpendicular to thesurface of the optical disk so as to move a focus of the light beam in athickness direction of the optical disk. In the focusing control, afocusing actuator that is composed of a voice coil motor, for example,is used for moving the converging lens. Once the focus of the light beamis positioned on the recording surface of the optical disk, the focusingactuator controls the movement of the converging lens to keep a distancebetween the recording surface and the converging lens substantiallyconstant (this corresponds to a state where a focusing servo isperformed).

[0004] In the focusing control, a relatively large driving current maybe applied to the focusing actuator continuously because of a breakdownof a circuit included in a focusing servo system or the like. When sucha large driving current continuously flows through the focusing actuatorover a time period longer than a predetermined time period, a powersupplied to the focusing actuator may exceed the maximum rating powerthereof, causing overheating of the focusing actuator. This overheatingmay cause the focusing actuator to be damaged.

[0005] As a method for protecting the actuator from being damaged, thereis a known method in which the driving of the focusing actuator isstopped when the driving current for the actuator exceeds apredetermined current value (Japanese Patent Publication No. 6-64745,for example). In accordance with the method, it is possible to determinethat the focusing actuator is driven abnormally in a case where thecurrent having the magnitude exceeding a predetermined magnitude iscontinuously applied to the focusing actuator, as shown in FIG. 1A, whenthe optical disk apparatus begins the operation or the focusing servo isperformed. Thus, the damage of the actuator can be prevented.

[0006] Moreover, when the focusing servo is performed, a transientdisturbance may occur because of a partial waver caused by a localundulation or unevenness of the recording surface of the optical diskgenerated in a fabrication process of the optical disk, a vibrationapplied to the optical disk apparatus or the like. In a case where thefocusing actuator is driven in order to suppress the aforementionedexternal disturbance, a driving current shown in FIG. 1B, for example,flows through the focusing actuator. By supplying such a driving currentto the focusing actuator, it is possible to make the movement of theconverging lens follow the waver of the optical disk, thus maintainingthe appropriate focusing state.

[0007] However, according to the aforementioned conventional method forprotecting the actuator, when the driving current shown in FIG. 1B issupplied to the focusing actuator, it is determined that the driving ofthe focusing actuator is in the abnormal state at a time at which thecurrent value exceeds the predetermined current value even if the powerdoes not exceed the maximum rating power expressed as the product of apredetermined time period (rating time) and a predetermined currentvalue (rating current), so that the driving of the focusing actuator isstopped. This prevents the supply of the driving current having anecessary magnitude to the focusing actuator, resulting in a failure ofthe focusing servo.

[0008] On the other hand, as a method of protecting the actuator, thereis another known method in which the driving current for the focusingactuator is integrated by using a predetermined time constant and thedriving of the focusing actuator is stopped when the integration result(that is, the power) exceeds a predetermined value (Japanese Patent No.2864799, for example). In accordance with this method, it is notdetermined that the driving of the focusing actuator is in the abnormalstate when the driving current shown in FIG. 1B flows through thefocusing actuator. Thus, it is possible to continue the focusing servo.

[0009] The latter protection method utilizes an integration technique (asigned value integration) in which an output of an integrator is alwaysapproximately zero in a case where the driving current goes between aplus side (charging) and a minus side (discharging). This is becausethis method takes a case of suppressing the disturbance in one direction(a direction in which the converging lens becomes closer to the opticaldisk or a direction opposite thereto) occurring at a periodsubstantially the same as the rotation period of the optical disk intoconsideration. In this case, in order to protect the actuator, it issufficient that the integration result of the current value when thedriving current corresponding to such a flash or transientunidirectional disturbance flows through the actuator is obtained.During a period in which no transient disturbance occurs (when thenormal servo is performed), the driving current fluctuates between thepositive and the negative while having the smaller amplitude. It ispreferable according to this conventional protection method that thedriving current when the normal servo is performed is not contained inthe current integration value used for determining whether or not thecondition for protecting the actuator is satisfied.

[0010] In recent years, the rotation speed of the optical disk in theoptical disk apparatus has been largely increased. However, this causesa problem of occurrence of an external disturbance having a highfrequency. It is known that the waver caused when the optical diskrotates contains not only a waver occurring in synchronization with onerotation of the optical disk (a primary component) but also a componentN times the primary component (a higher degree component). In a case ofrotating the optical disk at 160 Hz to 180 Hz, for example, the primarywaver having the frequency of 160 Hz to 180 Hz and a high frequencycomponent (the high-frequency disturbance) having 2 kHz to 3 kHz may begenerated. Such a high-frequency disturbance largely influences thefocusing servo.

[0011] Herein, the influences of the high-frequency disturbance on thefocusing servo are described.

[0012]FIG. 2 shows loop characteristics of the focusing servo system inthe conventional optical disk apparatus. The waver having a lowerfrequency and a large amplitude, such as the primary component of thewaver, is generated in a lower-frequency region (100 Hz or less, forexample). Thus, as shown with Line A in FIG. 2, it is necessary to setthe loop gain in the lower-frequency region to be a large value so as toimprove the ability of following the waver of the optical disk. Thisenables the focusing actuator to be driven in such a manner that adeviation of the focus from the recording surface is equal to or lessthan a predetermined level, thereby the focusing control can beperformed appropriately. On the other hand, the loop gain is set to be asmall value in a higher-frequency region (1 kHz or more, for example).This is because the amplitude of the high-frequency disturbance is small(for example, within a range where a signal can be read from the opticaldisk) and therefore there is no problem even if the gain of the servo ismade small.

[0013] When the optical disk is rotated at a higher speed, however, theexternal disturbance having the quite high frequency is generated. Thespectrum of such disturbance is shown in FIG. 2. As the amplitude ofsuch a high-frequency component becomes larger, there arises a necessityof making the loop gain of the focusing servo system relatively larger.Therefore, in the case of rotating the optical disk at the higher speed,the high-frequency disturbance having the large amplitude is suppressedby making the gain (loop gain) of the servo larger, as shown with Line Bin FIG. 2, to improve the following ability. Otherwise, the appropriatefocusing servo state cannot be maintained because of the high-frequencycomponent of the disturbance, preventing the continuousreproduction/recording operation.

[0014] In the case of the larger loop gain, however, the powerconsumption of the focusing actuator also becomes large. To the focusingactuator, the driving current containing the high-frequency componenthaving the large amplitude, for example, as shown in FIG. 1C, issupplied in order to follow the high-frequency disturbance. Such acurrent component fluctuates between the plus side and the minus side asthe driving current for suppressing the primary waver of the opticaldisk fluctuates. The current component is always applied to the focusingactuator when the focus servo is performed. This means that asubstantially constant additional power is supplied to the focusingactuator.

[0015] Therefore, when the optical disk is rotated at the higher speed,the large driving current containing a high-frequency AC component isapplied to the focusing actuator, thus the focusing actuator maycontinue to be driven abnormally. The adverse effect of the AC componentcontained in the driving current on the focusing actuator becomes largeras the rotation speed of the optical disk increases. Thehigher-frequency AC component of the driving current increases the powersupplied to the focusing actuator.

[0016] On the other hand, according to the latter one of theconventional protection methods mentioned above, the AC component of thedriving current fluctuating between the plus side and the minus sidethat is generated when the focusing servo is performed for the opticaldisk rotating at the higher speed cannot be detected. Thus, it isimpossible to determine whether or not the abnormal driving of thefocusing actuator occurs. Such a problem does not arise when the opticaldisk is rotated at a relatively low speed.

[0017] Moreover, the conventional optical disk apparatus protects theactuator by stopping the driving of the focusing actuator when detectingthe abnormal driving of the focusing actuator. Thus, there is a problemthat information recorded on a portion where the abnormal driving isdetected cannot be reproduced.

[0018] Furthermore, the conventional optical disk apparatus does nothave a protection function for a tracking actuator. Therefore, it isimpossible to detect an AC component of a large driving current appliedto the tracking actuator when the reproduction/recording operation isperformed for the optical disk eccentrically rotating at the higherspeed, as in the case of the focusing actuator. Accordingly, theabnormal driving of the tracking actuator cannot be detected. Theprotection of the tracking actuator is also important when the opticaldisk is rotated at the higher speed.

SUMMARY OF THE INVENTION

[0019] The invention provides an optical disk apparatus that can stablyperform the reproduction/recording operation for the optical disk whileprotecting the focusing/tracking actuator appropriately.

[0020] An inventive optical disk apparatus includes: a light irradiatoroperable to converge a light beam and irradiate an information carrierwith the converged light beam; a moving means operable to move aconverging point of the light beam in a direction substantiallyperpendicular to a surface of the information carrier; and a focusingcontroller operable to control the moving means to place the convergingpoint of the light beam at a predetermined position. The focusingcontroller includes: a converging state detector operable to generate adetection signal corresponding to a converging state of the light beamon the information carrier; a focusing driving means operable togenerate a driving signal for driving the moving means based on thedetection signal; an integrator operable to integrate a magnitude of asignal corresponding to the driving signal over a predetermined timeperiod; and an abnormal state detector operable to detect an abnormalstate of the moving means based on an output of the integrator.

[0021] Another inventive optical disk apparatus includes: a lightirradiator operable to converge a light beam and irradiate aninformation carrier with the converged light beam; a moving meansoperable to move a converging point of the light beam in a directionsubstantially perpendicular to a surface of the information carrier; anda focusing controller operable to control the moving means to place theconverging point of the light beam at a predetermined position. Thefocusing controller includes: a converging state detector operable togenerate a detection signal corresponding to a converging state of thelight beam on the information carrier; a focusing driving means operableto generate a driving signal for driving the moving means based on thedetection signal; an integrator operable to integrate a magnitude of asignal corresponding to the detection signal over a predetermined timeperiod; and an abnormal state detector operable to detect an abnormalstate of the moving means based on an output of the integrator.

[0022] In one embodiment of the present invention, the driving signal isdecreased to prevent the moving means from being damaged when theabnormal state detector detects the abnormal state of the moving means.

[0023] In another embodiment of the present invention, a loop gain ofthe focusing controller is decreased when the abnormal state detectordetects the abnormal state of the moving means.

[0024] In still another embodiment of the present invention, a rotationspeed of the information carrier is lowered when the abnormal statedetector detects the abnormal state of the moving means.

[0025] In yet another embodiment of the present invention, the opticaldisk apparatus further includes: a second moving means operable to movethe light beam in a direction traversing a track formed on the surfaceof the information carrier; a deviation detector operable to generate asignal corresponding to a positional relationship between the light beamand the track; and a tracking controller operable to control the lightbeam to scan on the track by driving the second moving means in responseto the signal generated by the deviation detector. The abnormal statedetector changes a detection threshold value used for detection of theabnormal state in accordance with operation modes of the trackingcontroller.

[0026] Still another inventive optical disk apparatus includes: a lightirradiator operable to converge a light beam and irradiate aninformation carrier with the converged light beam; a moving meansoperable to move the light beam in a direction traversing a track formedon a surface of the information carrier; a tracking controller operableto control the moving means to scan the track with the light beam. Thetracking controller includes: a deviation detector operable to generatea detection signal corresponding to a positional relationship betweenthe light beam on the information carrier and the track; a trackingdriving means operable to generate a driving signal for driving themoving means based on the detection signal; an integrator operable tointegrate a magnitude of a signal corresponding to the driving signalover a predetermined time period; and an abnormal state detectoroperable to detect an abnormal state of the moving means based on anoutput of the integrator.

[0027] Yet another inventive optical disk apparatus includes: a lightirradiator operable to converge a light beam and irradiate aninformation carrier with the converged light beam; a moving meansoperable to move the light beam in a direction traversing a track formedon a surface of the information carrier; a tracking controller operableto control the moving means to scan the track with the light beam. Thetracking controller includes: a deviation detector operable to generatea detection signal corresponding to a positional relationship betweenthe light beam on the information carrier and the track; a trackingdriving means operable to generate a driving signal for driving themoving means based on the detection signal; an integrator operable tointegrate a magnitude of a signal corresponding to the detection signalover a predetermined time period; and an abnormal state detectoroperable to detect an abnormal state of the moving means based on anoutput of the integrator.

[0028] In one embodiment of the present invention, the driving signal isdecreased to prevent the moving means from being damaged when theabnormal state detector detects the abnormal state of the moving means.

[0029] In another embodiment of the present invention, a loop gain ofthe tracking controller is decreased when the abnormal state detectordetects the abnormal state of the moving means.

[0030] In still another embodiment of the present invention, a rotationspeed of the information carrier is lowered when the abnormal statedetector detects the abnormal state of the moving means.

[0031] Yet another inventive optical disk apparatus includes: a lightirradiator operable to converge a light beam and irradiate aninformation carrier with the converged light beam; and a moving meansoperable to move a converging point of the light beam in a directionsubstantially perpendicular to a surface of the information carrier. Themagnitude of a focusing control signal is integrated over apredetermined time period, the focusing control signal being used forcontrolling a movement of the moving means to place the converging pointof the light beam at a predetermined position. A driving signal fordriving the moving means is adjusted based on a result of theintegration.

[0032] Yet another inventive optical disk apparatus includes: a lightirradiator operable to converge a light beam and irradiate aninformation carrier with the converged light beam; and a moving meansoperable to move the light beam in a direction traversing a track formedon a surface of the information carrier. The magnitude of a trackingcontrol signal is integrated over a predetermined time period, thetracking control signal being used for controlling a movement of themoving means to allow the light beam and the track to have apredetermined positional relationship. A driving signal for driving themoving means is adjusted based on a result of the integration.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0033] The foregoing summary as well as the following detaileddescription of the preferred embodiments of the invention, will bebetter understood when read in conjunction with the appended drawings.For the purpose of illustrating the invention, there is shown in thedrawings an embodiment which is presently preferred. It should beunderstood, however, that the invention is not limited to the precisearrangements and instrumentalities shown. In the drawings:

[0034]FIGS. 1A, 1B and 1C are diagrams showing a driving current for afocusing actuator; FIG. 1A shows a case where a continuous disturbanceoccurs; FIG. 1B shows a case where a flash or transient disturbanceoccurs; and FIG. 1C shows a case where a high frequency component of thedisturbance occurs;

[0035]FIG. 2 shows loop characteristics of a focusing servo system;

[0036]FIG. 3 is a block diagram illustrating a structure of an opticaldisk apparatus according to the first embodiment of the presentinvention;

[0037]FIG. 4 is a diagram schematically showing an exemplaryconfiguration for an optical head included in the optical disk apparatusof the present invention;

[0038]FIG. 5 is a flowchart illustrating an abnormal driving statedetection process for a focusing actuator in the first embodiment;

[0039]FIGS. 6A and 6B are flowcharts illustrating a process performedwhen the abnormal state is detected in the first embodiment; FIG. 6Aillustrates a case of lowering a rotation speed of an optical disk; FIG.6B illustrates a case of lowering a loop gain of a focusing controlsystem;

[0040]FIG. 7 is a block diagram illustrating a structure of an opticaldisk apparatus according to the second embodiment of the presentinvention;

[0041]FIG. 8 is a block diagram illustrating a structure of an opticaldisk apparatus according to the third embodiment of the presentinvention;

[0042]FIG. 9 is a flowchart illustrating an abnormal driving statedetection process for a tracking actuator in the third embodiment;

[0043]FIGS. 10A and 10B are flowcharts illustrating a process performedwhen the abnormal state is detected in the third embodiment; FIG. 10Aillustrates a case of lowering the rotation speed of the optical disk;FIG. 10B illustrates a case of lowering a loop gain of a trackingcontrol system;

[0044]FIG. 11 is a block diagram illustrating a structure of an opticaldisk apparatus according to the fourth embodiment of the presentinvention;

[0045]FIG. 12 is a block diagram illustrating a structure of an opticaldisk apparatus according to the fifth embodiment of the presentinvention;

[0046]FIG. 13 is a flowchart illustrating an abnormal driving statedetection process for an actuator in the fifth embodiment;

[0047]FIGS. 14A and 14B are flowcharts illustrating a process performedwhen the abnormal state is detected in the fifth embodiment; FIG. 14Aillustrates a case of lowering the rotation speed of the optical disk;FIG. 14B illustrates a case of lowering the loop gain of thefocusing/tracking control system;

[0048]FIG. 15 is a block diagram illustrating a structure of an opticaldisk apparatus according to the sixth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0049] Hereinafter, preferred embodiments of the inventive optical diskapparatus will be described with reference to the accompanying drawings.

[0050] (Embodiment 1)

[0051]FIG. 3 is a block diagram schematically showing the structure ofthe optical disk apparatus according to the first embodiment of thepresent invention.

[0052] The optical disk apparatus 100 of the present embodiment includesa disk motor 102 for rotating an optical disk 101 at a predeterminedrotation speed: an optical head 103 for reproducing information from theoptical disk 101 or recording information onto the optical disk 101; afocusing actuator 30 for moving a converging point of a light beamradiated by the optical head 103 to the optical disk 101 in a thicknessdirection of the optical disk 101 (i.e., a direction substantiallyperpendicular to a disk surface); and a focusing controller 150 forcontrolling the focusing actuator 30 to perform a focusing operation. Inaddition, the optical disk apparatus 100 includes a traverse motor (notshown) for moving the optical head 103 in a direction substantiallyperpendicular to a track direction provided on the optical disk 101(i.e., a radial direction of the optical disk 101).

[0053] With reference to FIG. 4, the optical head 103 is described. Theoptical head 103 includes a light source 10, such as a semiconductorlaser; a coupling leans 12; a polarized beam splitter 14: a polarizer16; a converging lens (an objective lens) 18; a condense lens 20; asplitting mirror 22; a photodetector 24 for focusing error detection;and a photodetector 26 for tracking error detection. The focusingactuator 30 associated with the optical head 103 is constituted by avoice coil motor including a magnet fixed to the converging lens and adriving coil provided near the magnet, for example. The focusingactuator 30 can move the converging lens 18 in the directionsubstantially perpendicular to the disk surface with high accuracy.

[0054] In the optical head 103, the light beam emitted from the lightsource 10 is changed to parallel rays by the coupling lens 12, reflectedby the polarized beam splitter 14 and then passes through the polarizer16 so as to be converged by the converging lens 18. The converged lightbeam is radiated to the optical disk 101 to form a focus (convergingpoint) F on a recording layer 101 a of the optical disk 101. Actually,the converging point F is a beam spot having a finite diameter and apredetermined focal depth. An appropriate converging state is realizedwhen the recording layer 101 a of the optical disk 101 is positioned atsuch a beam spot.

[0055] The light reflected from the optical disk 101 passes through theconverging lens 18, the polarizer 16, the polarized beam splitter 14 andthe condense lens 20 in that order, and is then divided by the splittingmirror 22 into light beams towards two directions. One of the lightbeams is input to the focusing controller 150 (see FIG. 3) via thephotodetector 24 for the focusing error detection (a two-dividedphotodetector in this embodiment), while the other light beam is inputto a tracking controller described later via the photodetector 26 forthe tracking error detection (a four-divided photodetector in thisembodiment).

[0056] It should be noted that the structure of the optical head 103 isnot limited to the above. The optical head 103 may include an opticalsystem (a light irradiator) having various configurations that canconverge the light beam and illuminate the optical disk with theconverged light beam. For example, instead of using the beam splitter, ahologram element having a diffraction grating may be used to generate anerror signal. Moreover, the optical system may be integrated to be asingle component by forming an element having a similar function to thatof the objective lens, a photodiode and the like on a substrate havingan optical guide layer by semiconductor processes. In addition, thefocusing actuator may have various configurations in accordance with theconfiguration of the optical head or the like, as long as the focusingactuator can move the converging point of the light beam in thedirection substantially perpendicular to the recording surface of theoptical disk.

[0057] Returning to FIG. 3, the focusing controller 150 includes afocusing error signal generator 104, a digital signal processor(hereinafter, simply referred to as a DSP) 114 and a focusing drivingcircuit 115.

[0058] In the focusing error signal generator 104, signals output fromthe two-divided photodetector 24 are input to a differential amplifierthat outputs to the DSP 114 a signal indicating a deviation of theconverging point of the light beam from the optical disk 101, i.e., afocusing error signal (hereinafter, referred to as an FE signal). Such adetection method of the FE signal is called as “SSD method”. Please notethat the FE signal can be detected by another detection method, such as“Knife-edge method.”

[0059] The FE signal input to the DSP 114, that is an analog signal, isconverted into a digital signal by an A/D converter 106. The digitalsignal from the A/D converter 106 is input to a phase compensationfilter 107 for compensating a phase of a focusing control system. Thephase compensation filter 107 is a digital filter constituted by anadder, a multiplier and a delay circuit. A focusing control signalhaving a phase compensated by the phase compensation filer 107 is inputto a gain changing circuit 108 for changing a loop gain of the focusingcontrol system. It should be noted that the term “focusing controlsignal” as used herein means various signals used for the focusingcontrol that contain information related to the focusing error. Thus,the “focusing control signal” may be analog or digital, includes the FEsignal, the digital signal processed in the DSP and a focusing actuatordriving signal (described later). The signal output from the gainchanging circuit 108 is then input to a switch 109 that switches theopening/closing of the loop of the focusing control system. The switch109 is turned on when the focusing control (the focusing servo) isperformed.

[0060] The focusing control signal that passed through the switch 109 isconverted from the digital signal to an analog signal by a D/A converter110 and is then input to a focusing driving circuit 115. The focusingcontrol signal input to the focusing driving circuit 115 is subjected toan appropriate current amplification and an appropriate leveladjustment, so that the focusing actuator driving signal is generated.Therefore, the focusing driving circuit 115 drives the focusing actuator30. Thus, the focusing actuator 30 is driven in such a manner that thelight beam on the optical disk 101 always in a predetermined convergingstate, thereby the focusing control is performed.

[0061] In the DSP 114, the focusing control signal that passed throughthe switch 109 is also input to an integrator 111. The integrator 111integrates a magnitude of the focusing control signal input thereto overa predetermined time period and outputs the integration result to acomparator 112. The comparator 112 compares the integration result fromthe integrator 111 with an abnormal state detection level (Fdlvl)determined by the CPU 105. When the integration result exceeds theabnormal state detection level (Fdlvl), it is determined that thefocusing actuator is in an abnormal driving state. In this case, asignal indicating that the focusing actuator is abnormally driven issent from an abnormal state detector 113 to the CPU 105. Actually, theseprocesses are performed in accordance with a program stored in theoptical disk apparatus.

[0062] Next, a process of detecting the abnormal driving state of thefocusing actuator is described referring to the block diagram of FIG. 3and a flowchart of FIG. 5.

[0063] A process executed by software in the DSP 114 is classified intoa main process where various types of abnormal states are checked andprocesses based on commands received from the CPU 105 are performed andan interrupting internal process in which a control of the disk motor,the focusing control and the tracking control and the like are performedin a constant sampling time period.

[0064] In Step S1 of the main process, the switch 109 is closed to startthe focusing control so that the light beam on the optical disk 101 isalways in a predetermined converging state. In Steps S2 and S3, afocusing driving integration value (Fdsum) and an abnormal statedetection counter (t) in the integrator 111 are initialized. Then, afunction of detecting the abnormal driving state of the focusingactuator is turned on in Step S4, thereby starting the integration ofthe magnitude of the focusing control signal in the integrator 111.

[0065] Then, in Step S5, it is checked whether or not the abnormal stateis detected. At this time, the main process goes into a state of waitinga next command sent from the CPU 105 where various processes can beperformed based on the commands from the CPU 105. On the other hand, themain processes waits for a signal indicative of the abnormal drivingstate of the focusing actuator from the interrupting internal process.Although the tracking control is started following the above process inthe actual optical disk apparatus, the description of the trackingcontrol is omitted.

[0066] At the state where the main process is waiting for the commandfrom the CPU 105 in Step S5, the interrupting internal process performsthe detection of the abnormal driving the focusing actuator. Thisdetection can be performed anytime in the DSP 114, as well as otherabnormal state detections (for example, the detection whether or not thefocusing servo can be turned on).

[0067] Next, the interrupting internal process is described. The DSP 114starts the following detection routine in the interrupting internalprocess, when the function of detecting the abnormal driving state ofthe focusing actuator is turned on in Step S4 of the main process.

[0068] In Step S6, it is determined whether or not the abnormal statedetection counter (t) reaches a predetermined detection time (T). In acase where the counter (t) does not reach the predetermined detectiontime (T), the absolute or unsigned value (i.e., magnitude) of thecurrent focusing control signal for the focusing actuator that haspassed through the switch 109 is added to the current focusing drivingintegration value (Fdsum) in Step S7, thereby the focusing drivingintegration value (Fdsum) is updated. Moreover, the abnormal statedetection counter (t) is increased in Step S8, and then the process goesback to Step S6.

[0069] In a case where the abnormal state detection counter (t) reachesthe predetermined time (T) in Step S6, the focusing driving integrationvalue (Fdsum) is compared with the abnormal state detection level(Fdlvl) set in the comparator 112 by the CPU 105, in Step S9. When thefocusing driving integration value (Fdsum) does not exceed the abnormalstate detection level (Fdlvl), the abnormal state detection counter (t)and the focusing driving integration value (Fdsum) are reset to zero inSteps S10 and S11, then returning to Step S6. On the other hand, whenthe focusing driving integration value (Fdsum) exceeds the abnormalstate detection level (Fdlvl), it is determined that the focusingactuator is driven abnormally in Step S12, notifying that to the mainprocess. The main process then notifies the CPU 105 via the abnormalstate detector 113 that the focusing actuator is driven abnormally.

[0070] The predetermined detection time (T) and the abnormal statedetection level (Fdlvl) mentioned above are appropriately set based on,for example, the maximum rated power of the actuator (continuously 1W orless and 2W or less in two seconds, for example). It is preferable thatthe predetermined detection time (T) is equal to or longer than a periodof the rotation of the optical disk and is equal to or shorter than arating time defining the maximum rating power of the actuator. In a casewhere the detection time (T) is shorter than the rotation period of theoptical disk, there is a possibility that effects of a disturbance whichmay occur in synchronization with the rotation period of the opticaldisk is not reflected to the integration result. In this case, theaccuracy of the abnormal state detection is lowered. In another casewhere the detection time (T) exceeds the rating time of the actuator,there is a possibility that the power exceeding the maximum rating powerof the actuator may be supplied to the actuator in the abnormal state.Therefore, the detection time (T) exceeding the rating time of theactuator is not appropriate for protecting the actuator.

[0071] Next, a process following the process of detecting the abnormaldriving state of the focusing actuator in the present embodiment isdescribed referring to the block diagram of FIG. 3 and flowcharts ofFIGS. 6A and 6B.

[0072]FIGS. 6A is a flowchart in a case of protecting the focusingactuator by lowering the rotation speed of the disk motor 102, whileFIG. 6B is a flowchart in a case of protecting the focusing actuator bylowering the loop gain of the focusing control system.

[0073] First, the case of lowering the rotation speed of the disk motor102 is described. As shown in FIG. 6A, it is determined whether or notthe focusing actuator is driven abnormally in Step S20. When thefocusing actuator is driven normally, the process goes back to Step S20.The detection of the abnormal state of the focusing actuator driving isperformed by the abnormal state detector 113 in the DSP 114 as describedabove, and the detection result is notified to the CPU 105 when theabnormal state is detected. The CPU 105 that received the notificationfrom the DSP 114 reduces the rotation speed of the disk motor 102 inStep S21. The magnitude of the power supplied to the focusing actuatorin order to track the waver of the surface of the optical disk 101 is inproportion to a square of the rotation speed of the disk motor 102.Thus, when the rotation speed of the disk motor 102 is reduced, it ispossible to largely decrease the power supplied to the focusing actuator(that is, to make the magnitude of the focusing actuator driving signalsmaller). In this way, the focusing actuator can be appropriatelyprotected by lowering the rotation speed of the disk motor 102 in such amanner that the focusing driving integration value (Fdsum) does notexceed the abnormal state detection level (Fdlvl).

[0074] In addition, when the rotation speed of the optical disk isreduced as described above, a frequency of an external disturbance (highdegree components of the waver of the disk surface, for example) is alsolowered, thus securing the loop gain sufficient for the focusing servosystem. Therefore, the focusing servo control is kept in an appropriatestate and the reproduction/recording of the optical disk can beperformed continuously.

[0075] Next, the case of lowering the loop gain of the focusing controlsystem is described. As shown in FIG. 6B, it is determined whether ornot the focusing actuator is driven abnormally in Step S22. When thefocusing actuator is driven normally, the process goes back to Step S22.When the focusing actuator is driven abnormally, the setting of the gainchanging circuit 108 is changed so as to make the loop gain of thefocusing control system smaller in such a manner that the focusingdriving integration value (Fdsum) does not exceed the abnormal statedetection level (Fdlvl) in Step S23. Thus, the power supplied to theactuator is decreased, thereby the actuator can be protected.

[0076] Moreover, when both the rotation speed of the optical disk andthe loop gain of the focusing control system are lowered, it is possiblenot only to protect the focusing actuator but also to keep the focusingservo control in the appropriate state effectively. In a case oflowering the rotation speed of the optical disk only, the loop gainremains relatively large although the disturbance having the highfrequency is reduced. Therefore, the focusing servo system is in a statehaving a tracking ability equal to or larger than the necessary trackingability. Such a state is disadvantageous in reducing a driving currentof the actuator. On the other hand, when both the rotation speed of theoptical disk and the loop gain are lowered, the power consumption of theactuator can be reduced effectively while the appropriate servoperformance is realized.

[0077] Such an operation of lowering both the rotation speed of theoptical disk and the loop gain of the focusing control system can beeasily realized by changing the reproduction/recording modes that may beprovided with the optical disk apparatus. The optical disk apparatus mayhave, as the reproduction/recording modes, a plurality of differentmodes that have different rotation speeds of the optical disk. There isa known optical disk apparatus having a plurality of mode of 48 x, 40 x,32 x, 24 x, 8 x and the like. For each mode, the loop gain is set inadvance to a value appropriate for the rotation speed of that mode. Amode controller provided with the optical disk apparatus can freelychange the loop gain as well as the rotation speed of the optical disk.

[0078] Therefore, by controlling the mode selection so that the currentmode is changed to the next mode having the lower rotation speed thanthat of the current mode in the case where the driving of the focusingactuator is detected to be in the abnormal state when the focusingcontrol is performed, not only the rotation speed of the optical diskbut also the loop gain of the focusing control system can beappropriately lowered. Thus, the continuous reproduction/recording canbe performed while the actuator is protected.

[0079] In addition, if the abnormal state is detected even when the modeis changed to the next mode so as to lower the rotation speed to apredetermined rotation speed, it is preferable to further change themode to the next mode having the lower rotation speed than that of thecurrent mode. Moreover, when the mode is changed so as to lower therotation speed of the optical disk, the mode does not go back to the“old” mode.

[0080] Furthermore, when the rotation speed is relatively low (24 x or 8x, for example), the loop gain of the focusing control system is set toa small value and therefore the power exceeding the acceptable power ofthe actuator is not supplied to the actuator in most cases. Thus, insuch modes, the function of detecting the abnormal driving state may bemade inoperative. In this case, even in the environment where theabnormal driving of the actuator occurs when the optical disk is rotatedat a high speed, the reproduction/recording operation can be reliablyperformed in the mode having the lower rotation speed. Accordingly, thedriving of the actuator can be prevented from stopping, thus providing acomfortable environment of use.

[0081] As described above, according to the present embodiment, even inthe case where the focusing actuator is detected to be drivenabnormally, the actuator can be protected from being damaged and thereproduction/recording operation for the optical disk can be performedcontinuously. In particular, when a mode changing operation is used, thecontinuous reproduction/recording operation can be easily performedwhile the actuator is protected appropriately. This is very effective inpractical use.

[0082] In the above description, the focusing control in the opticaldisk apparatus 100 is described. Also, the tracking control is performedin the optical disk apparatus 100. In the tracking controller (notshown), a deviation signal, i.e., a tracking error signal (hereinafter,referred to as a TE signal) is generated for indicating a deviation ofthe converging point of the light beam on the optical disk 101 from thetarget track by using the signals from the photodetector 26 (see FIG.4). Based on the TE signal, a tracking actuator is controlled in such amanner that the target track is scanned with the converging point of thelight beam on the optical disk 101. The details of the configuration ofthe tracking controller and the tracking control operation will bedescribed in another embodiment.

[0083] The abnormal state detection level (Fdlvl) is described as aconstant level regardless of a state of the tracking control in thepresent embodiment. However, when the abnormal state detection level(Fdlvl) is changed between a state where the tracking control is on,such as a state of a normal reproduction, and a state where the trackingcontrol is off, such as a state of a searching operation, the focusingactuator can be more appropriately protected.

[0084] Such a change of the abnormal state detection level is effectivein a case where the maximum rating power of the actuator is defined bythe sum of the power supplied to the focusing actuator and that suppliedto the tracking actuator. When the tracking control is not performed,the power supplied to the tracking actuator is zero. At this time, evenif a relatively large power is supplied to the focusing actuator, theactuator is not damaged. Therefore, the abnormal state detection level(Fdlvl) for the focusing control can be set relatively high. On theother hand, a predetermined magnitude of the power is supplied to thetracking actuator when the tracking control is performed. Thus, it isnecessary to set the abnormal state detection level (Fdlvl) to arelatively low level and to reduce the acceptable power supplied to thefocusing actuator. In this way, the actuator can be appropriatelyprotected.

[0085] As described above, according to the present embodiment, themagnitude of the signal corresponding to the driving signal of thefocusing actuator is integrated over the predetermined time period, andbased on the integration result the abnormal state of the focusingactuator driving is detected. In the case where the abnormal state isdetected, the rotation speed of the optical disk is reduced or the loopgain of the focusing control system is lowered so as to make themagnitude of the signal for driving the focusing actuator smaller,thereby controlling the power supplied to the focusing actuator.Therefore, the focusing actuator can be appropriately protected againstan AC component (see FIG. 1C) of the large driving current occurringwhen the reproduction/recording operation is performed for the diskrotating at a higher speed with waver. Moreover, thereproduction/recording operation can be performed stably.

[0086] It should be noted that the above-mentioned manner of protectionof the focusing actuator can be applied not only when information isreproduced from the optical disk but also when information is recordedonto the optical disk. The optical disk apparatus of the presentembodiment may be a recordable/reproducible optical disk apparatus, areproduction-only optical disk apparatus or a recording-only opticaldisk apparatus. In addition, the optical disk apparatus of the presentembodiment can be used for performing the recording/reproductionoperation for various types of optical disks including a recording layerhaving a state that is changeable by the radiation of the light beam (aphase-change layer, a magneto-optical medium layer or the like).

[0087] (Embodiment 2)

[0088]FIG. 7 is a block diagram schematically showing the structure ofan optical disk apparatus 200 according to the second embodiment of thepresent invention. The optical disk apparatus 200 is different from theoptical disk apparatus 100 of the first embodiment in that an integrator201 for integrating a magnitude of the FE signal that has been convertedto the digital signal by the A/D converter 106 over a predetermined timeperiod is provided in place of the integrator 111. In the presentembodiment, a signal corresponding to the FE signal is used fordetecting the abnormal driving state of the focusing actuator, unlikethe first embodiment in which the signal corresponding to the drivingsignal for the focusing actuator is used. The same components as thosedescribed in the first embodiment are labeled with the same referencenumerals and the detailed description thereof is omitted in the presentembodiment.

[0089] The FE signal that has been digitalized by passing through theA/D converter 106 is input to the integrator 201 that integrates themagnitude of the FE signal over a predetermined time period to outputthe integration result to the comparator 112. The comparator 112compares the integration result from the integrator 201 with theabnormal state detection level (Felvl) set by the CPU 105. When theintegration result exceeds the abnormal state detection level (Felvl),it is determined that the focusing actuator is driven abnormally. Thus,the abnormal state detector 113 sends the CPU 105 the signal indicativeof the abnormal state.

[0090] The process of detecting the abnormal driving state of thefocusing actuator in the present embodiment is the same as that in thefirst embodiment except that the signal corresponding to the FE signalis used for the abnormal state detection, instead of the signalcorresponding to the driving signal for the focusing actuator. Thus, thedetailed description of the detection process is omitted.

[0091] When the abnormal driving state of the focusing actuator isdetected after the magnitude of the digital FE signal is integrated overthe predetermined time period, the operation of lowering the rotationspeed of the optical disk and/or the operation of lowering the loop gainof the focusing control is performed, as in the first embodiment. Thisrealizes the stable reproduction/recording operation while the focusingactuator is protected appropriately against the AC component of thelarge driving current occurring when the recording/reproducing isperformed for the optical disk rotating at a higher speed with waver.

[0092] In addition, as in the first embodiment, the actuator can beprotected more appropriately by changing the abnormal state detectionlevel (Felvl) between the state where the tracking control is on, suchas the state where the normal reproduction is performed, and the statewhere the tracking control is off, such as the state where the searchoperation is performed.

[0093] (Embodiment 3)

[0094]FIG. 8 is a block diagram schematically showing the structure ofan optical disk apparatus 300 according to the third embodiment of thepresent invention. In the third embodiment, the method of detecting theabnormal state that is applied for protecting the focusing actuator inthe first embodiment is applied to the tracking actuator. The samecomponents as those described in the first embodiment are labeled withthe same reference numerals and the detailed description thereof isomitted in the present embodiment.

[0095] The optical disk apparatus 300 includes the disk motor 102 forrotating the optical disk 101 at a predetermined rotation speed; anoptical head 103 for reproducing/recording information from/onto theoptical disk 101; a tracking actuator 40 for moving the light beamradiated from the optical head 103 to the optical disk 101 in adirection traversing the track provided on the optical disk 101; and atracking controller 350 for controlling the tracking actuator 40 to scana predetermined track with the light beam. In addition, the optical diskapparatus 300 includes the traverse motor (not shown) for moving thewhole optical head 103 in such a direction that the optical head 103traverses the track.

[0096] As the tracking actuator 40, a device that can pivotally move theconverging lens in a plane substantially parallel to the surface of theoptical disk may be used, for example. It should be noted that the trackscanned by the optical disk apparatus 300 is, for example, a grooveformed on the surface of the optical disk, a land formed between thegrooves, or both of the groove and the land.

[0097] The tracking controller 350 includes a tracking error signalgenerator 301, a digital signal processor (DSP) 310, and a trackingdriving circuit 311.

[0098] To the tracking error signal generator 301 is input the outputsignals from the four-divided photodetector 26 (see FIG. 4). Thetracking error signal generator 301 adds the signals output from twodiagonal detecting parts of the four-divided photodetector 26. Also, thesignals from other two diagonal detecting parts are added to each other.The resultant signals are sliced in a comparator to be binary signals,respectively. The sliced signals are input to a phase comparator thatcompares the phases of the sliced signals. The phase comparator outputsa signal corresponding to the advance or delay of the phase to adifferential amplifier. An output signal from the differential amplifierindicates a deviation of the converging point of the light beam on theoptical disk 101 from the track. The thus generated signal is called thetracking error signal (TE signal) and is input to the DSP 310. Theoptical disk apparatus 300 controls the tracking actuator 40 based onthe TE signal in such a manner that the target track is scanned with theconverging point of the light beam on the optical disk 101. Theabove-mentioned detection method of the TE signal is called as “Phasedifference method.” Please note that the TE signal may be detected byanother detection method, such as “Push-pull method.”

[0099] The TE signal input to the DSP 310, that is analog, isdigitalized by the A/D converter 302 and is then input to a phasecompensation filter 303 that is a digital filter constituted by anadder, a multiplier and a delay circuit. The phase compensation filter303 compensates the phase of the tracking control system. A trackingcontrol signal having the phase compensated by the phase compensationfilter 303 is input to a gain changing circuit 304 for changing a loopgain of the tracking control system. Please note that the term “trackingcontrol signal” as used herein means various signals used for thetracking control that contain information related to the tracking error.Thus, the “tracking control signal” may include the TE signal mentionedabove, the digital signal processed in the DSP, a tracking actuatordriving signal (described later) and may be analog or digital. Thesignal output from the gain changing circuit 304 is then input to aswitch 305 for opening/closing the loop of the tracking control system.The switch 305 is turned on when the tracking control (tracking servo)is performed.

[0100] The tracking control signal (digital signal) that passed throughthe switch 305 is converted to an analog signal by the D/A converter306, and is then input to the tracking driving circuit 311. In thetracking driving circuit 311, the tracking control signal is subjectedto an appropriate current amplification and an appropriate leveladjustment, so that a tracking actuator driving signal is generated. Inthis way, the tracking driving circuit 311 drives the tracking actuator40. Therefore, the tracking actuator 40 is driven in such a manner thata predetermined track is scanned with the converging point of the lightbeam on the optical disk 101, realizing the tracking control.

[0101] Preferably, the driving of the traverse motor is also controlledso that the converging point of the light beam on the optical disk 101is coincident with the center of the converging lens (that is, anoptical axis of the light beam radiated to the optical disk 101 iscoincident with an optical axis of the converging lens), when the trackis scanned with the converging point of the light beam.

[0102] The tracking control signal that passed through the switch 305 isalso input to the integrator 307 that integrates the magnitude of thetracking control signal input thereto over a predetermined time periodso as to output the integration result to a comparator 308. Thecomparator 308 compares the integration result from the integrator 307with an abnormal state detection level (Tdlvl) determined by the CPU105. When the integration result exceeds the abnormal state detectionlevel (Tdlvl), it is determined that the tracking actuator is drivenabnormally. Thus, an abnormal state detector 309 sends the CPU 105 asignal indicating that the tracking actuator is driven abnormally.

[0103] Next, a process of detecting the abnormal state of the trackingactuator driving in the present embodiment is described, referring toFIGS. 8 and 9. FIG. 9 is a flowchart of the detection process.

[0104] A process executed by software in the DSP 310 is composed of themain process and the interrupting internal process, as described in thefirst embodiment. In Step S30 of the main process, the switch 305 isclosed, thus starting the tracking control to scan a predetermined trackwith the converging point of the light beam on the optical disk 101. InSteps S31 and S32, a tracking driving integration value (Tdsum) and anabnormal state detection counter (t) in the integrator 307 areinitialized. A function of detecting the abnormal state of the trackingactuator driving is then turned on in Step S33, thereby starting theintegration of the magnitude of the tracking control signalcorresponding to the driving signal for the tracking actuator in theintegrator 307.

[0105] Then, it is checked whether or not the abnormal state is detectedin Step S34. At this time, the main process is in a state of waiting anext command from the CPU 105. Although in the actual optical diskapparatus the focusing control has to be performed in advance of thestart of the tracking control, the description thereof is omitted in thepresent embodiment.

[0106] The interrupting internal process is described below. When thefunction of detecting the abnormal state of the tracking actuatordriving is turned on in Step S33 of the main process, the DSP 310 startsthe following detection routine in the interrupting internal process.

[0107] In Step S35, it is determined whether or not the abnormal statedetection counter (t) reaches a predetermined detection time (T). Whenthe counter (t) does not reach the predetermined detection time (T), anabsolute value or unsigned value (i.e., magnitude) of a current trackingcontrol signal that has passed through the switch 305 is added to thecurrent tracking driving integration value (Tdsum) in Step S36, therebyupdating the tracking driving integration value (Tdsum). Moreover, theabnormal state detection counter (t) is also updated in Step S37, andthen the process goes back to Step S35.

[0108] When the abnormal state detection counter (t) reaches thepredetermined detection time (t) in Step S35, the tracking drivingintegration value (Tdsum) is compared with the abnormal state detectionlevel (Tdlvl) set in the comparator 308 by the CPU 105, in Step S38. Ina case where the tracking driving integration value (Tdsum) does notexceed the abnormal state detection level (Tdlvl), the abnormal statedetection counter (t) and the tracking driving integration value (Tdsum)are reset to zero in Steps S39 and S40, respectively, and then theprocess goes back to Step S35. In another case where the trackingdriving integration value (Tdsum) exceeds the abnormal state detectionlevel (TdIvl), it is determined that the tracking actuator is drivenabnormally in Step S41, thus notifying that to the main process. Themain process notifies the CPU 105 via the abnormal state detector 309that the driving of the tracking actuator is in the abnormal state.Please note that the predetermined detection time (T) and the abnormalstate detection level (Tdlvl) are set appropriately in advance based on,for example, the maximum rating power of the actuator (continuously 1Wor less and 2W or less in two seconds, for example) and the like, as inthe first embodiment.

[0109] Next, a process after the abnormal driving of the trackingactuator is detected in the present embodiment is described, referringto FIGS. 10A and 10B showing the flows of the process, in addition toFIG. 8.

[0110]FIG. 10A is a flowchart in a case of protecting the trackingactuator by lowering the rotation speed of the disk motor 102, whileFIG. 10B is a flowchart in a case of protecting the tracking actuator bylowering the loop gain of the tracking control system.

[0111] First, the case of lowering the rotation speed of the disk motor102 is described. As shown in FIG. 10A, it is determined whether or notthe driving of the tracking actuator is in the abnormal state in StepS50. When the tracking actuator is driven normally, the process goesback to Step S50. The detection of the abnormal state is performed bythe abnormal state detector 309 in the DSP 310 as described above, andthe detection result is notified to the CPU 105. The CPU 105 receivingfrom the DSP 310 the notification that the driving of the trackingactuator is in the abnormal state reduces the rotation speed of the diskmotor 102 in Step S51. The magnitude of the power supplied to thetracking actuator in order to follow an eccentric rotation of theoptical disk 101 is in proportion to a square of the rotation speed ofthe disk motor 102. Thus, the power supplied to the tracking actuatorcan be largely reduced (that is, the magnitude of the tracking actuatordriving signal can be reduced) by lowering the rotation speed of thedisk motor 102. Therefore, the tracking actuator can be appropriatelyprotected by lowering the rotation speed of the disk motor 102 so thatthe tracking driving integration value (Tdsum) does not exceed theabnormal state detection level (Tdlvl). In addition, since the trackingservo can be kept in the appropriate state, the reproduction/recordingoperation for the optical disk can be performed continuously.

[0112] Next, the case of lowering the loop gain of the tracking controlsystem is described. As shown in FIG. 10B, it is determined whether ornot the driving of the tracking actuator is in the abnormal state inStep S52. When the tracking actuator is driven normally, the processgoes back to Step S52. On the other hand, when the tracking actuator isdriven abnormally, the setting of the gain changing circuit 304 ischanged so as to lower the loop gain of the tracking control system insuch a manner that the tracking driving integration value (Tdsum) doesnot exceed the abnormal state detection level (Tdlvl) in Step S53. Thus,the power supplied to the tracking actuator is reduced, therebyprotecting the actuator.

[0113] In addition, also in the present embodiment, when both of therotation speed of the optical disk but also the loop gain of thetracking control system are lowered, the power supplied to the actuatorcan be effectively reduced while the appropriate tracking servo isrealized, as in the first embodiment. Such an operation can be realizedby changing the modes of the optical disk apparatus.

[0114] As described above, according to the present embodiment, thesignal corresponding to the driving signal for the tracking actuator issubjected to the magnitude integration over a predetermined time period,and based on the integration result the abnormal state of the driving ofthe tracking actuator can be detected. When the abnormal state isdetected, the magnitude of the signal for driving the tracking actuatoris made smaller by lowering the rotation speed of the optical disk orthe loop gain of the tracking control system, thereby the power suppliedto the tracking actuator is controlled. In this way, the trackingactuator can be protected appropriately against the AC component of thelarge driving current occurring when the reproduction/recordingoperation is performed for the optical disk eccentrically rotating at ahigher speed.

[0115] Moreover, in the above description, the embodiment in which thetracking actuator for tracking and the transverse motor for moving thewhole optical head are provided as separate components is described.However, instead of using the tracking actuator and the transversemotor, a moving means having both the functions mentioned above (amoving mechanism having a swing arm, for example) can be used.

[0116] (Embodiment 4)

[0117]FIG. 11 is a block diagram schematically showing the structure ofan optical disk apparatus 400 according to the fourth embodiment of thepresent invention. The optical disk apparatus 400 is different from theoptical disk apparatus 300 of the third embodiment in that an integrator401 that integrates over a predetermined time period the magnitude ofthe TE signal digitalized in the A/D converter 302, in place of theintegrator 307. In the present embodiment, a signal corresponding to theTE signal is used for detecting the abnormal state of the driving of thetracking actuator, instead of the signal corresponding to the drivingsignal for the tracking actuator in the third embodiment. The samecomponents as those described in the third embodiment are labeled withthe same reference numerals and the detailed description thereof isomitted in the present embodiment.

[0118] The TE signal that has been digitalized by passing through theA/D converter 302 is input to the integrator 401. The integrator 401integrates the magnitude of the TE signal over a predetermined timeperiod and outputs the integration result to the comparator 308. Thecomparator 308 compares the integration result from the integrator 401with the abnormal state detection level (Telvl) set by the CPU 105. Whenthe integration result exceeds the abnormal state detection level(Telvl), the driving of the tracking actuator is determined to be in theabnormal state. In this case, the abnormal state detector 309 sends theCPU 105 the signal indicative of the abnormal state.

[0119] The process of detecting the abnormal state of the trackingactuator driving and the process following the detection process in thepresent embodiment are the same as those in the third embodiment exceptthat the signal corresponding to the TE signal is used for the detectionof the abnormal state, instead of the signal corresponding to thedriving signal for the tracking actuator. Therefore, the detaileddescription of the processes is omitted in the present embodiment.

[0120] According to the present embodiment, the signal corresponding tothe TE signal is subjected to the magnitude integration over apredetermined time period, and based on the integration result theabnormal state of the driving of the tracking actuator is detected. Inthe case where the abnormal state is detected, the magnitude of thedriving signal for the tracking actuator is reduced by lowering therotation speed of the optical disk and/or lowering the loop gain of thetracking control system, thereby controlling the power supplied to thetracking actuator. Therefore, the tracking actuator can be protectedappropriately against the AC component of the large driving currentoccurring when the reproduction/recording operation is performed for theoptical disk eccentrically rotating at a higher speed. In addition, thereproduction/recording operation can be performed stably.

[0121] (Embodiment 5)

[0122]FIG. 12 is a block diagram schematically showing the structure ofan optical disk apparatus 500 according to the fifth embodiment of thepresent invention. The optical disk apparatus 500 is realized bycombining the structure of the optical disk apparatus 100 of the firstembodiment (see FIG. 3) and that of the optical disk apparatus 300 (seeFIG. 8). The same components as those described in the first and thirdembodiments are labeled with the same reference numerals and thedetailed description thereof is omitted in the present embodiment.

[0123] In the optical disk apparatus 500, the signals from thephotodetector 24 for the focusing error detection (see FIG. 4) in theoptical head 103 are input to the focusing error signal generator 104,while the signals from the photodetector 26 for the tracking errordetection (see FIG. 4) are input to the tracking error signal generator301. The focusing error signal generator 104 and the tracking errorsignal generator 301 generate the FE signal for the focusing control andthe TE signal for the tracking control, respectively. The optical diskapparatus 500 controls the focusing actuator 30 and the trackingactuator 40 based on the FE signal and the TE signal, respectively.

[0124] In the focusing control system, the focusing control signal thatpassed through the switch 109 provided in a DSP 501 is input to theintegrator 111. The integrator 111 integrates the magnitude of thefocusing control signal over a predetermined time period and outputs theintegration result to the comparator 112. The comparator 112 comparesthe integration result from the integrator 111 with the abnormal statedetection level (Fdlvl) set by the CPU 105. When the integration resultexceeds the abnormal state detection level (Fdlvl), the driving of thefocusing actuator is determined to be in the abnormal state. Thus, theabnormal state detector 113 sends the CPU 105 the signal indicating thatthe driving of the focusing actuator is in the abnormal state.

[0125] In the tracking control system, the tracking control signal thatpassed through the switch 305 is input to the integrator 307. Theintegrator 307 integrates the magnitude of the tracking control signalover a predetermined time period and outputs the integration result tothe comparator 308. The comparator 308 compares the integration resultfrom the integrator 307 with the abnormal state detection level (Tdlvl)set by the CPU 105. When the integration result exceeds the abnormalstate detection level (Tdlvl), the driving of the tracking actuator isdetermined to be in the abnormal state. Thus, the abnormal statedetector 309 sends the CPU 105 the signal indicating that the driving ofthe tracking actuator is in the abnormal state.

[0126] Herein, the process of detecting the abnormal driving state inthe present embodiment is described in detail, referring to the blockdiagram of FIG. 12 and the flowchart of FIG. 13.

[0127] The process executed by software in the DSP 501 is composed ofthe main process and the interrupting internal process, as described inthe first embodiment.

[0128] In Step S60 of the main process, the switch 109 is closed therebystarting the focusing control in such a manner that the light beam onthe optical disk 101 always has a predetermined converging state. Then,in Steps S61 and S62, the focusing driving integration value (Fdsum) inthe integrator 111, the tracking driving integration value (Tdsum) inthe integrator 307 and the abnormal state detection counter (t) areinitialized. The function of detecting the abnormal driving state of thefocusing actuator is then turned on in Step S63, thereby starting theintegration of the magnitude of the focusing control signal in theintegrator 111.

[0129] Then, the switch 305 is closed in Step S64, so as to start thetracking control in such a manner that a predetermined track is scannedwith the converging spot of the light beam on the optical disk 101. Whenthe function of detecting the abnormal driving state of the trackingactuator is turned on in Step S65, the integration of the magnitude ofthe tracking control signal is started in the integrator 307. Then, itis checked whether or not the abnormal state is detected in Step S66,while main process goes to the state of waiting the next command fromthe CPU 105.

[0130] The DSP 501 starts the following detection routine in theinterrupting internal process when the function of detecting theabnormal driving state of the focusing actuator and the function ofdetecting the abnormal driving state of the tracking actuator are turnedon in Steps S63 and S65 of the main process, respectively.

[0131] It is determined whether or not the abnormal state detectioncounter (t) reaches the predetermined detection time (T) in Step S67. Inthe case where the counter (t) does not reach the predetermineddetection time (T), the magnitude of the current focusing control signalthat has passed through the switch 109 is added to the current focusingdriving integration value (Fdsum) in Step S68, thereby the focusingdriving integration value (Fdsum) is updated. Similarly, the magnitudeof the current tracking control signal that has passed through theswitch 305 is added to the tracking driving integration value (Tdsum),thereby updating the tracking driving integration value (Tdsum).Moreover, the abnormal state detection counter (t) is also updated(i.e., is increased) in Step S69, and thereafter the process goes backto Step S67.

[0132] In the case where the abnormal state detection counter (t)reaches the predetermined detection time (T) in Step S67, the focusingdriving integration value (Fdsum) and the abnormal state detection level(Fdlvl) set in the comparator 112 by the CPU 105 are compared with eachother in Step S70. When the focusing driving integration value (Fdsum)exceeds the abnormal state detection level for the focusing actuator(Fdlvl), the driving of the focusing actuator is determined to be in theabnormal state in Step S71, notifying that to the main process. The mainprocess then notifies the CPU 105 via the abnormal state detector 113that the focusing actuator is driven abnormally. On the other hand, whenthe focusing driving integration value (Fdsum) does not exceed theabnormal state detection level (Fdlvl), the tracking driving integrationvalue (Tdsum) and the abnormal state detection level for the trackingactuator (Tdlvl) set in the comparator 308 by the CPU 105 are comparedwith each other. When the tracking driving integration value (Tdsum)does not exceed the abnormal state detection level (Tdlvl), the abnormalstate detection counter (t), the focusing driving integration value(Fdsum) and the tracking driving integration value (Tdsum) are reset tozero, and the process goes back to Step S67. On the other hand, when thetracking driving integration value (Tdsum) exceeds the abnormal statedetection level (Tdlvl), it is determined that the tracking actuator isdriven abnormally in Step S75, notifying that to the main process. Themain process that has received the notification notifies the CPU 105 viathe abnormal state detector 309.

[0133] The predetermined detection time (T) and the abnormal statedetection levels (Fdlvl and Tdlvl) in the above description areappropriately set based on, for example, the maximum rating power of theactuator (continuously 1W or less and 2W or less in two seconds, forexample).

[0134] Next, the process following the detection of the abnormal statein the present embodiment is described, referring to the block diagramof FIG. 13 and flowcharts of FIGS. 14A and 14B.

[0135]FIG. 14A is the flowchart in the case of protecting thefocusing/tracking actuator by lowering the rotation speed of the diskmotor 102, while FIG. 14B is the flowchart in the case of protecting thefocusing/tracking actuator by lowering the loop gain of the focusingand/or tracking control system.

[0136] First, the case of lowering the rotation speed of the disk motor102 is described. As shown in FIG. 14A, it is determined whether or notthe abnormal state of the focusing actuator driving occurs in Step S80.When the abnormal driving state of the focusing actuator does not occur,it is then determined whether or not the abnormal driving state of thetracking actuator occurs in Step S81. If the abnormal state is notdetermined to occur in Step S81, the process goes back to Step S80. Whenthe CPU 105 received the notification of the abnormal state for eitherthe focusing actuator or the tracking actuator from the DSP 501 in StepS80 or S81, the CPU 105 reduces the rotation speed of the disk motor102. More specifically, in the case of the abnormal state of thefocusing actuator driving, the rotation speed of the disk motor 102 isreduced in such a manner that the focusing driving integration value(Fdsum) does not exceed the abnormal state detection level (Fdlvl) inStep S82. In the case of the abnormal state of the tracking actuatordriving, the rotation speed of the disk motor 102 is reduced in such amanner that the tracking driving integration value (Tdsum) does notexceed the abnormal state detection level (Tdlvl) in Step S82. Thus, thereproduction/recording operation can be performed for the optical disk101 stably, while the focusing/tracking actuator is protectedappropriately.

[0137] Next, the case of reducing the loop gain of the focusing/trackingcontrol system is described. As shown in FIG. 14B, it is determinedwhether or not the abnormal state of the focusing actuator drivingoccurs in Step S83. When the abnormal state does not occur, it is thendetermined whether or not the abnormal state of the tracking actuatordriving occurs in Step S84. If the abnormal driving state of thetracking actuator is not determined to occur in Step S84, the processgoes back to Step S83. When the CPU 105 received the notification of theabnormal state for the focusing actuator from the DSP 501 in Step S83,the CPU 105 changes the setting of the gain changing circuit 108 so asto make the loop gain of the focusing control system smaller in such amanner that the focusing driving integration value (Fdsum) does notexceed the abnormal state detection level (Fdlvl) in Step S85. On theother hand, when the CPU 105 received the notification of the abnormalstate for the tracking actuator from the DSP 501 in Step S84, the CPU105 changes the setting of the gain changing circuit 304 so as to makethe loop gain of the tracking control system smaller in such a mannerthat the tracking driving integration value (Tdsum) does not exceed theabnormal state detection level (Tdlvl) in Step S86. Thus, the powersupplied to the focusing/tracking actuator can be reduced, thereby theactuator can be protected.

[0138] Moreover, also in the present embodiment, when both the rotationspeed of the optical disk and the loop gain of the focusing/trackingcontrol system are lowered at the same time, the power supplied to theactuator can be effectively reduced while the focusing/tracking servo iskept in the appropriate state, as in the first embodiment. Such anoperation can be performed by changing the operation mode of the opticaldisk apparatus.

[0139] As described above, according to the present embodiment, thesignal corresponding to the driving signal for the focusing/trackingactuator is subjected to the magnitude integration over a predeterminedtime period, and based on the integration result the abnormal drivingstate of the focusing/tracking actuator can be detected. When theabnormal state is detected, the magnitude of the signal for driving thefocusing/tracking actuator is made smaller by lowering the rotationspeed of the optical disk or the loop gain of either one of the focusingcontrol system and the tracking control system that corresponds to theactuator in the abnormal driving state, thereby the power supplied tothe actuator in the abnormal driving state can be controlled. Thus, theactuator can be protected appropriately against the AC component of thelarge driving current occurring when the reproduction/recordingoperation is performed for the optical disk with waiver rotating at thehigher speed or the optical disk eccentrically rotating at the higherspeed. Moreover, the stable reproduction/recording operation can berealized.

[0140] In addition, in the case where the maximum rating power of theactuator is defined by the sum of the power supplied to the focusingactuator and that supplied to the tracking actuator, the abnormal statedetection level for the focusing actuator (Fdlvl) may be changed inaccordance with the operation state of the tracking control system, asdescribed in the first embodiment. This enables more appropriateprotection of the focusing actuator.

[0141] (Embodiment 6)

[0142]FIG. 15 is a block diagram schematically showing the structure ofan optical disk apparatus 600 according to the sixth embodiment of thepresent invention. The optical disk apparatus 600 is realized bycombining the structure of the optical disk apparatus 200 of the secondembodiment (see FIG. 7) and that of the optical disk apparatus 400 (seeFIG. 11). The same components as those described in the second andfourth embodiments are labeled with the same reference numerals and thedetailed description thereof is omitted in the present invention.

[0143] In the focusing control system, the FE signal that passed throughthe A/D converter 106 is input to the integrator 201. The integrator 201integrates the magnitude of the FE signal over a predetermined timeperiod and outputs the integration result to the comparator 112. Thecomparator 112 compares the integration result from the integrator 201with the abnormal state detection level (Felvi) set by the CPU 105. Whenthe integration result exceeds the abnormal state detection level(Felvl), the driving of the focusing actuator is determined to be in theabnormal state. Thus, the abnormal state detector 113 sends the CPU 105the signal indicating that the driving of the focusing actuator is inthe abnormal state.

[0144] In the tracking control system, the TE signal that passed throughthe A/D converter 302 is input to the integrator 401. The integrator 401integrates the magnitude of the TE signal over a predetermined timeperiod and outputs the integration result to the comparator 308. Thecomparator 308 compares the integration result from the integrator 401with the abnormal state detection level (Telvi) set by the CPU 105. Whenthe integration result exceeds the abnormal state detection level(Telvl), the driving of the tracking actuator is determined to be in theabnormal state. Thus, the abnormal state detector 309 sends the CPU 105the signal indicating that the driving of the tracking actuator is inthe abnormal state.

[0145] The process of detecting the abnormal driving state and theprocess following the detection process in the present embodiment arethe same as those in the fifth embodiment except that the signalcorresponding to the FE/TE signal is used for the detection of theabnormal state, instead of the signal corresponding to the drivingsignal for the focusing/tracking actuator. Therefore, the detaileddescription of the processes is omitted in the present embodiment.

[0146] According to the present embodiment, the signal corresponding tothe FE/TE signal is subjected to the magnitude integration over apredetermined time period, and based on the integration result theabnormal driving state of the focusing/tracking actuator is detected. Inthe case where the abnormal state is detected, the magnitude of thedriving signal for the focusing/tracking actuator is reduced by loweringthe rotation speed of the optical disk and/or lowering the loop gain ofeither one of the focusing control system and the tracking controlsystem that corresponds to the actuator driven abnormally, therebycontrolling the power supplied to the actuator. Therefore, the actuatorcan be protected appropriately against the AC component of the largedriving current occurring when the reproduction/recording operation isperformed for the optical disk with waiver rotating at the higher speedor the optical disk eccentrically rotating at the higher speed. Inaddition, the stable reproduction/recording operation can be performed.

[0147] Moreover, as in the fifth embodiment, when the abnormal statedetection level for the focusing actuator (Felvl) is changed between thestate where the tracking control is on, such as the state of the normalreproduction, and the state where the tracking control is off, such asthe state where the search operation is performed, the focusing actuatorcan be protected more appropriately.

[0148] In the above description, the embodiments in which theintegration of the magnitude of the focusing/tracking control signal andthe detection of the abnormal driving state of the actuator based on theintegration result are performed using the DSP in accordance with theprogram are described as the first through sixth embodiments. However,the configuration of the optical disk apparatus of the present inventionis not limited thereto. The optical disk apparatus of the presentinvention may include an analog circuit having the configurationallowing the integration of the magnitude of the focusing/trackingcontrol signal and the detection of the abnormal driving state of theactuator based on the integration result, without using the DSP.

[0149] Moreover, as the signal process conducted in the DSP, varioustypes of signal processes can be applied as long as they can integratethe magnitude of the focusing/tracking control signal and then detectthe abnormal driving state of the actuator based on the integrationresult.

[0150] As described above, according to the present invention, when thefocusing control is performed, the magnitude of the focusing controlsignal for controlling the converging point of the light beam (thedriving signal for the focusing actuator, the focusing error signal, orthe signal corresponding to these signals) is integrated over apredetermined time period. Then, the abnormal driving state of thefocusing actuator is detected based on the magnitude integration. Whenthe abnormal driving state is detected, the signal for driving thefocusing actuator (the driving current) is reduced by lowering therotation speed of the optical disk and/or lowering the loop gain of thefocusing control system. Therefore, the stable reproduction/recordingoperation can be performed while the focusing actuator is protectedappropriately.

[0151] Also, when the tracking control is performed, the magnitude ofthe tracking control signal for controlling a positional relationshipbetween the converging point of the light beam and the target track (thedriving signal for the tracking actuator, the tracking error signal, orthe signal corresponding to these signals) is integrated over apredetermined time period. Then, the abnormal driving state of thetracking actuator is detected based on the magnitude integration. Whenthe abnormal driving state is detected, the signal for driving thetracking actuator (the driving current) is reduced by lowering therotation speed of the optical disk or and/or lowering the loop gain ofthe tracking control system. Therefore, the stablereproduction/recording operation can be performed while the trackingactuator is protected appropriately.

[0152] While the present invention has been described in a preferredembodiment, it will be apparent to those skilled in the art that thedisclosed invention may be modified in numerous ways and may assume manyembodiments other than that specifically set out and described above.Accordingly, it is intended by the appended claims to cover allmodifications of the invention which fall within the true spirit andscope of the invention.

We claim:
 1. An optical disk apparatus comprising: a light irradiatoroperable to converge a light beam and irradiate an information carrierwith the converged light beam; a moving means operable to move the lightbeam in a direction traversing a track formed on a surface of theinformation carrier; and a tracking controller operable to control themoving means to scan the track with the light beam, wherein the trackingcontroller includes: a deviation detector operable to generate adetection signal corresponding to a positional relationship between thelight beam on the information carrier and the track; a tracking drivingmeans operable to generate a driving signal for driving the moving meansbased on the detection signal; an integrator operable to integrate amagnitude of a signal corresponding to the driving signal over apredetermined time period, and an abnormal state detector operable todetect an abnormal state of the moving means based on an output of theintegrator.
 2. An optical disk apparatus according to claim 1, whereinthe driving signal is decreased to prevent the moving means from beingdamaged when the abnormal state detector detects the abnormal state ofthe moving means.
 3. An optical disk apparatus according to claim 2,wherein a loop gain of the tracking controller is decreased when theabnormal state detector detects the abnormal state of the moving means.4. An optical disk apparatus according to claim 2, wherein a rotationspeed of the information carrier is lowered when the abnormal statedetector detects the abnormal state of the moving means.
 5. An opticaldisk apparatus comprising: a light irradiator operable to converge alight beam and irradiate an information carrier with the converged lightbeam; a moving means operable to move the light beam in a directiontraversing a track formed on a surface of the information carrier; and atracking controller operable to control the moving means to scan thetrack with the light beam, wherein the tracking controller includes: adeviation detector operable to generate a detection signal correspondingto a positional relationship between the light beam on the informationcarrier and the track; a tracking driving means operable to generate adriving signal for driving the moving means based on the detectionsignal; an integrator operable to integrate a magnitude of a signalcorresponding to the detection signal over a predetermined time period,and an abnormal state detector operable to detect an abnormal state ofthe moving means based on an output of the integrator.
 6. An opticaldisk apparatus according to claim 5, wherein the driving signal isdecreased to prevent the moving means from being damaged when theabnormal state detector detects the abnormal state of the moving means.7. An optical disk apparatus according to claim 6, wherein a loop gainof the tracking controller is decreased when the abnormal state detectordetects the abnormal state of the moving means.
 8. An optical diskapparatus according to claim 6, wherein a rotation speed of theinformation carrier is lowered when the abnormal state detector detectsthe abnormal state of the moving means.
 9. An optical disk apparatuscomprising: a light irradiator operable to converge a light beam andirradiate an information carrier with the converged light beam; and amoving means operable to move the light beam in a direction traversing atrack formed on a surface of the information carrier, wherein amagnitude of a tracking control signal is integrated over apredetermined time period, the tracking control signal being used forcontrolling movement of the moving means to allow the light beam and thetrack to have a predetermined positional relationship, and wherein adriving signal for driving the moving means is adjusted based on aresult of the integration.